The invention relates to a method for connecting contact surfaces of electrical component blanks, in particular contact surfaces on substrates having an electrically insulating surface and a layer resistor located thereon, with at least two extended, metallic connecting leads of a connection lead blank, which are first connected mechanically to each other by at least two cross-struts arranged spaced from each other in the connection lead blank. The invention also relates to a device for carrying out the method.
As component blanks, both single type semi-finished component products as well as continuous multiple type semi-finished component products are identified, which are separated into discrete components after their connection with connection leads. The latter are also designated as multi-component blanks (i.e., multi-unit plates).
From German Utility Model G 89 13 803.1 U1, a resistance thermometer is known for measuring surface temperature using a metal film temperature sensor, which is arranged in a plastic housing of an electronic power component with a cooling surface. The connection, which is constructed as a cooling unit of the electronic component and provided with a bore, forms the carrier or support for the metal film temperature sensor, wherein the connection surfaces of the metal layer temperature sensor are connected by bonding wires with the connections provided for the electronic power element. The housing is bounded by the metal surface of the connection used as a support and the plastic sheath, which surrounds the metal layer temperature sensor and the contact points of the bonding wires with the outwardly-guided connections. The bonding wires located between the connection surfaces of the sensor and the contact points of the connections are preferably made of gold, silver, platinum, or aluminum, and are preferably connected in an electrically conducting manner by thermo-compression bonding with connection surfaces and contact points. The relatively complicated manufacturing technology for the connection using bonding wires has proven to be problematic, since here, in addition to the adhesion of the sensor element to a connection, the additional contacting between connection surfaces and contact points is necessary. Furthermore, the temperature stability at higher temperatures is considered to be problematic.
An object of the invention is to make available in a cost-effective manner connection wires or bands on bonding pads, which produce an electrically and mechanically firm connection to the sensor element, wherein a corrosion resistance up to 750xc2x0 C. is provided.
This object is achieved according to the method in that in a first step for manufacturing a connection lead blank, openings are made in continuous metal sheet, which border the later cross-struts and connection leads of the connection lead blank. In a second step, the connection lead blank is brought into a cassette and seized there, such that one of the cross-struts projects out of the cassette (or cassette mouth) and is separated in a third step, in such a way that free ends of parallel-running connection leads project out of the cassette (or cassette mouth). In a fourth step, the cassette is brought into a bonding or welding device, so that the free ends of the connection leads are brought to cover the respective connection surfaces of at least one component blank or multi-component blank, and are connected to each other by a temperature-assisted bonding operation or by welding.
It has proven to be advantageous that, according to the method of the invention, sensor elements (or their contact surfaces) can be provided both as single units and as multi-component blanks with corresponding connection leads, wherein a largely automated manufacturing and further processing is possible.
In a preferred embodiment of the method, elongated, slot-shaped openings for the connection lead blank are etched from the metal sheet in the first step. In another embodiment of the method, elongated, slot-shaped openings for the connection lead blank are punched from the metal sheet in the first step. Furthermore, it is advantageously also possible to cut the elongated, slot-shaped openings for the connection lead blank from the metal sheet using a laser beam or a high pressure water jet, or a combination thereof.
Preferably, in the first step, openings for seizing the connection lead blank in the cassette and targeted breaking points for further processing are formed simultaneously.
In a preferred embodiment of the method, in the third step, the cross-strut is separated by mechanical stressing of the targeted breaking points or targeted breaking lines in the connection lead blank.
In the fourth step of the method, the free ends of the connection lead blank are advantageously brought together to cover the contact surfaces of a single type blank or of a multi-unit blank provided with targeted breaking points for separating blanks and are then bonded or welded, wherein the multi-unit blank is subsequently separated into individual blanks. Here, the free ends of the connection lead are advantageously connected together with the contact surfaces or bonding pads of the components by thermo-compression bonding or welding. At the conclusion of the fourth step, the second cross-strut is separated from the connection lead blank so that individual components result.
The method according to the invention has proven to be especially advantageous in regard to an automated processing or subsequent processing for large piece counts. In particular, a considerable cost-efficiency is to be achieved the manufacture and joining of band-shaped connection leads for multi-component blanks (parallel production in multi-units), since a connection lead blank is joined as a so-called xe2x80x9cmulti-band etching partxe2x80x9d or xe2x80x9cleadframexe2x80x9d to a complete series of individual component blanks or to a multi-component blank.
The object of the invention is achieved by a device in that, for receiving the connection lead blank manufactured according to the first step, a cassette having a lower part and an upper part is provided with a planar bearing surface for the connection lead blank, wherein bumps and/or pins project at least from the plane of the bearing surface for the purpose of orienting the connection lead blank by means of the openings located therein for the purpose of seizing it, wherein for the form-fit seizing of the cassette upper part, recesses are provided corresponding to the bumps.
It has proven to be especially advantageous that using the device, an exact positioning and dimensioning is possible by striking elements and beveled elements. In this manner, an inexact positioning of the connection lead blank is prevented.
In a preferred embodiment of the device, a separation device has a receiving device for the cassette, for the purpose of defined separation of a first cross-strut projecting from a first end of the cassette. A separation stamp is provided as a bending-aid, whose movement path cuts the planar bearing surface at an angle of 85 to 95xc2x0. Advantageously, the plane of the movement path of the separation stamp cuts the connection lead blank in the region of a targeted breaking point (or targeted breaking line).
Furthermore, in a preferred embodiment for performing the fourth step, the device has a bonding device or welding device with an assembly for form-fit reception of the cassette, wherein the cassette can be inserted with its first end adjacent to a heating plate, and the heating plate has a bearing surface for component blanks or a multi-component blank.
As a material for the connection lead, nickel or a nickel-based alloy is preferably used. Furthermore, it is possible to use stainless steel and silver or a silver-based alloy for the connection lead. The thickness of the connection lead blank lies in the range of about 0.05 to 0.6 mm, preferably about 0.15 to 0.25 mm.